Chain guard



D. M. KING Nov. 7, 1950 CHAIN GUARD 2 Sheets-Sheet 1 Filed NOV. 14, 1946 'fm enior 00mm Mm? Kma M0,

NOV. 7, 1950 7 mm, K 2,529,084

CHAIN GUARD Amewfar gay/4m M045? A74 W WVr Patented Nov. 7, 1950 "CHAIN GUARD henna Mayfe'r King, Hitcliin, England; assignor fOf-biIe-hfllfftfl King Limitedfiitchin;

" "England; a company of (g at Britain A lication-November 14, 1546g-Serial-No; 709,744 ---IniGr'eat-Britain March25yl-fi42 sec de-1, Public Law at, August 3; 1946 Patent'expires March-25', 1962 This'invention relates to guards for protecting loaded chains and is more particularly concerned with load chain guards for use with electric pulley hoist blocks.

."One object of the inventionresides -in the provision' of aload chain-guard which is adapted,- in the' event of the chain leaving its supporting sprocket,- to'be displaced, thereby avoiding dam- I agetothechain or'giiard. l A- further object of the invention is to provide a -load chain guard which, byico-opration with" the operation of' a sw'itch, "automatically controls the hoist motor.

' i ln- 'accorda'nce -with the invention the guardomprises a rockable arm orlikejel ement ar-; ranged; to fitabout a "portion of the hoist chain passing around the 'hoist fblocksprocket and u'fged't'owardsthe'cliain, and-means for normally preventing '-engagement o'f {the-farm with the chain; 3 The guard elementfl maybe pivotally mounted intermediate" its ends in' a carrier which is preferably 'removablyf supported in a holder s ecured between" the sidewalls of the hoist frame.

Tlieholder' may also be arranged tQ'fla CQOmmO-i date a switch in the hoist motor "circuit said switch being act'uabIe normallyto' closesaid circuit asby-an abutment on the guard element.

V A spring or 'springs'havingpne end attached to theigiiard-element' and the other tofa part ofthe hoist-frame or, where a second guard element is provided at the other side of the load chain sprocket'to the corresponding part c'ifsaidjsetz- 7 0nd guard, may be employednormally to hold tl ife guard'or guards in' operative position in proxv iinity to the chain.

I n" ord e'r" that 'the invention 'may be: clearly un i defr'stood and'readily carried into efiectth'ejsame will hereinafter be more; fully described. with.

is mounted for; pivotal-movement abouti'an axis:

tween the'zplateS 5'4", It and in'p'roximity'toxthe lower circumferential portion "of the sprocket l 0' by Fwhi'cli' the descending runof the chain-"isv caused to disengage from the? sprocket v gArranged between-the' side walls 'or plates 14 of the hoist block "are a' pair, of chain guard elmerits, one at: either side ofe th'esprocket mandeach;-,comprisi-ng an'arm 2t havingupper and lower; relatively" angularly inclined portions '2]; and :22 respectively; The upper portion -21 of;- each arm is shaped" to conform to the curvature 12 th-ejsp rocket and:th-is portion, furthermore, is

grooyedmii recessed on; itsinner faceas; indicated atv2i3 3 to receivevthe outer: portions of the; alter nate radially projecting links of the 1 load: chain.

' flach -of the chainguards is journalled inter mediate-its 1 ends for rocking movementabout" a pin-ifl' mountcd in' a' carrier 25 and each carrier is removabl-yf supported in' aholder26 secured in anyeconvenient manner, for example by rivets,-;

betweenthe side plates of the hoist block. The

carrier 25 comprises a substantially H-shaped casting having depending ears or lugs 21,- 21

V v bored to receive the pin 24, and upwardly extendreierenc'e' to the'accompanying drawings, in

Whifi offapulley hoist blo'ck fitted with a pair ofload chain guards in accordance 'with the invention, the near hoist frame side, wall'bi'ei'ng' omitted for Cl i y; V

" Eigure 2 is an end elevation of Figure' 1;

Figure 3 is a detail section on-line III-flier Figure 1; and.

Figure 4 is a detached, perspectiveview of the carrier retaining key,

Refer-ring to the drawings, to designates the drivingsprocket of achain hoist bloclr-to which rotary movement may be imparted in one direction or theother as by means of an-electric motor (not-shown). The'--1oad -chainll, as i1- r 40 Figure 1 isv a side elevation, pa'rtly'in section,

ing side portionsza, 28: which in the assembled position -project between side walls 29, 29 of the holder :25; :As shown more clearly in-Fig-ure"3,-

the upper ends of the upwardly extending side portionsifi of the 'carrierare outwardly flanged at;3i3,- 30 ,the carrier being held-in-positionin the holder:- by a U-shaped key 3i theside arms-32,

32 ofwhichengageb-etween the-flanges 3L-30 of the carrier and the-upper-faces of theside walls of-the holder- 25. The-key 3| has an-angularly bent portion 33 at its outer end. whichengages against the corresponding end-ofthe holder and by which; it linay be removably'secured to said: holder by a bolt 34. Each pin 2d isheld against p axial movement by the spaced side walls :or plates-0f the hoist frame. 7 V

Movement of the'guards towards the sprocket is limited by an adjustable stop in the form of-a bolt 35 threaded-into the lower or'h'eel end of eaehv g uardand adapted to abut against "a p'ro-' j ection. 36 on; eaclrofthe holders "to preventthe upperparts 21 of the guards coming into frictional contact with the chain. A lock nut 35a is provided to lock each of the bolts 35 in adjusted position. i

For the purpose of maintaining the guards in operative position closely adjacent the chain, springs 40 are stretched between the upper ends of the arms. Each of the springs is connected to the guard arms by buckles 4l-attached toop-f posite ends of the springs and each having a pin 42 adapted to engage in an open-ended slot 43 in the upper end of each arm. The springs are such. as to permit the arms to be deflected by the chain 7 into a retracted position, as shown in'broken lines in Figure 1, if the chain should become displaced with relation to the sprocket, thereby to avoid damage either to the chain or to the guards. Furthermore, the connection of the springs 40 to the guard arms enables said springs to be quickly detached from said arms to provide access to the chain and sprocket.

. Each of the holders 26 may also carry a switch (not: shown) of any appropriate kind, said switches being interposed in the circuit of the hoist motor or in a control circuit therefor. Preferably, however, these switches are of the open type provided with a plunger attachment having an appreciable over-run. Normally each of the switches is held in closed position by means of an abutment in the form of a bolt 44 carried at the lowerend of the corresponding guard arm and adapted in the operative position of the guard 'to engage a'. plunger 45 by which the switch is actuated. A lock nut 46is provided for holding the bolt 44 in adjusted position. Wheneitherof the guards is displaced by the chain, the" abutment 44 disengages from the plunger 45 and breaks the hoist motor circuit or control" circuit, and where, as shown, two guard members'are employed, eachswitch may be arranged to control the operation of the hoist motor in one direction only, so that said motor'may be carrier element, a removable key engageable with portions on said holder and said carrier element releasably to secure the latter in position in the holder,.re silient means connected to said arm at a point displaced from its pivot point and adapted to urge said arm towards the chain, an adjustable stozp'member associated with said arm at the opposite side of its pivot point to that at which the resilient means are connected and a rigid stop member with which said adjustable stop member is adapted to co-operate to limit the extent of the movement of the arm towards the chain under the action of said resilient means.

3. In a hoistpulley blockincluding a hoist block frame and a chain sprocket rotatably mounted'in said frame and around whichthe hoist chain passes, a chain guard comprising in combination a -holder fixedly mounted in the hoist block frame, a carrier element removably mounted in said holder, a removable key adapted to lock said carrier element in position in the holder, an arm mounted for pivotal movement, at a point between its ends, on said carrier element, said arm having a portion shaped tofit around asection of the chain as it passes around the sprocket, resilient means connected to said arm at a point; displaced from its pivot point and adapted to .urge .the same towards thechain. an adjustable stop member associated with said arm at the opposite side of. its pivot point to that at which theresilient-means are:connected, an-

. abutment-on the holder withwhich -said adjust- 10 able stop member is-adapted to co-operateto limit the ,extentof .the movement of,the;,ar1 n;

, towards the; chain. under-the .action of 1 the re,-

reversedto facilitate re-assembly ofthe' chain.)

'Alte'rnate ly, eachof the switches'may be arranged completely :to break the hoist motor Lc'ircuit or control circuitthereby to prevent actuation of the driving sprocket in either direction until the guards are returned to their operativepositions.

" 1 fIna hoist pull'ey block including a hoist termediate its ends, resilient means connected to said arm at a point displaced from its :pivot point and adapted to'urge said arm towards the chain, 1

an adjustable stop member associated with said arm' at the opposite side of its pivot point to that at which the resilient means are connected and a rigid stop member with which said adjustable stop'membe r is adapted to co-operate to limit the extent of the movement of the arm towards the' chain under the action of said resilient means.

2. In' a hoist pulley block including a hoist block frame and a chain sprocket rotatably mounted in said frame and around which the silient means, aswitch member: in the. [circuit of. an electric motor for operating the hoist sprocket;

- and means associated with said arm andadapted,

to control the,'operation' of'said-switch. I A

4. In a'hoist pulley. block including a hoist block. frame and a chain sprocket rotatably mounted in said frame and around which the hoist chain passes, a chain guard comprising combination a' pair" of arms disposed one at either side'of'the sprocketand each including a portionshaped to fit about a section of the. chain as it passes aroundthe sprocket, a pair of' carrier elements on each of which one of the arms is mounted for pivotal movement at afpointin termediat-efit's ends, resilient-means interposed between the arms and adapted to'urgethe same} towards each other and towards the chain,,a pair. of adjustable stop-members associated one with each arm and a pair f rigid stop memberswith each ofwhich one pf said adjustable stop mem bers 'isadapted to c0-operate to limit the extentof the movement. of the arms toward the ,chain under the action of the resilient means. 1'.

5. Ina hoist. pulley block including a ,h'oi's't' block frame and a chain. sprocket "rotatably mounted in said frame and aroundlwhich jthe hoist chain passes, a chain guard comprising .in combination apair of arms disposed one fat either side of the sprocket and each including an upper portion and a lower portion said upper portion being shaped to fit about a section of the chain as it passes around the sprocket, a pair of carrier elements on each of which one of" the armsmounted for pivotal movement at a point intermediate said upper and lower portions, a pair of holders fixedly mounted in the.

hoist block frame and each adapted to support a carrier element, a removable key in respect of each holder and carrier element and adaptedito lock said element releasably in position in the holder, resilient means interposed between the upper portions of the arms and adapted to urge the same towards each other and towards the chain, a pair of adjustable stop members associated ne with the lower portion of each arm and an abutment on each hold-er with each of which one of said adjustable stop members is adapted to co-operate to limit the extent of the movement of the arms towards the chain under the action of the resilient means.

6. In a hoist pulley block including a hoist block frame and a chain sprocket rotatably mounted in said frame and around which the hoist chain passes, a chain guard as in claim 5 in which an electric switch is associated with each holder and meansare associated with the lower portion of each arm to control the operation of said switches. I

DONALD MAYER KING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 349,520 Samuel Sept. 21, 1886 641,141 Lyon Jan. 20, 1900 647,242 Sprague Apr. 10, 1900 1,572,001 Dotzert Feb. 9, 1926 1,764,887 Posey June 17, 1930 

